The History of Circle

The circle has existed since prehistoric times. Invention of the wheel is the fundamental discoveries of the nature of the circle.The Greeks regarded Egypt as the inventor of geometry. ScribeAhmes, the author of the Rhind papyrus, provides rules fordetermining the area of a circle corresponding to π = 256 / 81 or about 3.16.

The first theorem relating to the circle that is associated with Thales around 650 BC. Book III of Euclid's Elements deals withthe nature and problem of inscribing circles and polygonsescribing.

One of the problems of Greek mathematics is a matter of finding the square with the same area as a given circle. Some of the'famous curves in a stack was first studied in an attempt to solvethis problem. In 450 BC Anaxagoras was the first recoredmathematicians to study this problem.

Problem to find a wide circle of cause of integration. For a circlewith the formula given above this region π ^ 2 and the length of acurve is 2π.
Pedal circle is the cardioid if the pedal point on thecircumference and is taken limacon if the point on the circumference of the pedal instead.

caustic of a circle with a point on the circumference is a cardioidshine, while if the beam is parallel to the caustic nephroid.

Apollonius, in about 240 BC, effectively demonstrated that thebipolar equation r = kr 'is a system of coaxial circles as k varies.In the case of bipolar equation mr + nr ^ 2 ^ 2 = c ^ 2 is a circlewhose center dividing line segment between two fixed points of the system in the ratio of n to m.

sources:
http://www-history.mcs.st-and.ac.uk/Curves/Circle.html